Electrochemical Stability of p ‐ GaInP2 in Aqueous Electrolytes Toward Photoelectrochemical Water Splitting

With an eye toward developing a photoelectrochemical system for water splitting using p ‐ GaInP 2 , the electrochemical stability of p ‐ GaInP 2 was studied in 10 M KOH, 3 M H 2 SO 4 , and a phosphate buffer of pH 7. It was found that in the dark, the p ‐ GaInP 2 electrode is susceptible to corrosion in all investigated solutions. Upon illumination, the anodic corrosion current increases. Under cathodic polarization in 10 M KOH, the p ‐ GaInP 2 electrode shows saturated photocurrent density, however the photocurrent slowly decreases with time due to the precipitation of an indium‐enriched oxide. In 3 M H 2 SO 4 , the anodic process can be inhibited under relatively low cathodic potentials, and stable photocurrents can be obtained. In neutral solution, p ‐ GaInP 2 is covered by a semi‐insulating oxide film and the observed photocurrent densities are much lower than those in 10 M KOH and 3 M H 2 SO 4 .